Speed control for dynamoelectric apparatus



Sept. 21 1948. mEs- 2,449,779

SPE ED CONTBOL FOR DYNAMOELECTRIC APPARATUS Filed Feb. 21, 1947 2 Sheets-Sheet 1 p 1948. R. JAESCHKE %4 3 A SEED COITROL FOR DYNAIOELECTRIC APPARATUS Filed Feb. 21, 1947 2 Sheets-Sheet 2 ta." w

Patented Sept. 21, 1948 &449379 sraan cos'rao. go

a DYNAMOELECTBIC mms Ralph L. Jechke, Kenola. w., sgoto Martin P. Winther, Waukean, m., a trustee Application February 21,1947, SerllNo. 736.059

e o (Ci. 172-234) This invention relates to speed controls for dynamoelectric apparatus and more particularly to electronic speed controls adapted to maintain substantially constant the speed oi' a rotating element of dynamoelectric apparatus.

Among the several objects of the invention may be noted the provision of simpler and less costiy means for remotely or otherwise regulating the speed of dynamoelectric apparatus (including very 'high-speed apparatus of thi type) under varying load conditions; the provision of means for easily accomplishing this end 'either in the case of newly designed apparatus, or as an attachment to previously designed apparatus; .and the provision of means of the class described for automatically controlling dynamoelectricapparatus at a desired speed and for selecting said desired speed. Other objects will be in part apparent and in part pointed out herelnafter.

This invention accordingly comprises the'elements and combinations of elements, features of construction, and arrangements of parts which will be exemplied in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in'which several of various possible embodiments of the invention are illustrated.

Fig. l is a schematic diagram of one embodi'- ment of the present invention;

Fig. 2 is a schematic diagramof an alternative embodiment; e

Fig. 3 is a side elevation of a, dynamoelectric apparatus illustratng another embodiment; and,

Figs 4, 5 and 6 schematically illustrate other embodiments. I

similar reference charactersindicate corresponding parts throughout the several views of the drawings.

As'. shown in U. S. Patent 2,277,284, it has been known to control the excitation of the field con of dynamoelectric machines such as eddy-current clutches and the like for controlling their speeds by using as a control the electric output' of' an A. C. generator driven from the output shaft of the machine. This is a successful method but whereon the present invention is an improvement. The generator element of the patent is best organized with the dynamoelectric machine when the latter is initially designed; whereas the corresponding elements of the present invention may be easily applied after the machine i designed. and on old machines. Furthernore, certain embodiments of the present invention are better adapted to certain newer high-speed dynamo- 2 electrlc machines Operating, say, at speeds of the order of mono-30,000 R. P. M. Greater flexibility and simplicity of design are ail'orded by means of the present invention.

Referring now more particularly to Fig. 1, there is shown at numeral I an electromagnetic slip coupling unit comprising a driving member 3 and a driven member I. The driven member 5 carries an exciter coil or field winding 'i which is adapted to be electrically energized through slip rings 9 and-wlres ll and II. An output or driven shaft i! is mechanically connected to the driven unit 5 and carries a simple two-segment 'commutator unit A. The commutator pick-up unit A is adapted' through a circuit, to be described below, to control the excitation of the coil 'I in such a manner as to control the degree of electromagnetic coupling between elements 3 and 5 so as to maintain substantially constant the speed 'of the driven shaft |5.' v

The electrical circuit of F e. 1 has, for purposes of description, been subdlvided into` three coop-` erative electronic circuit sections. circuit section I has as its function the variable energization of winding 1, the latter in eflect serving as a D. C.. load for circuit I. circuit II, a frequ'encydiscriminatory or responslve conversion circuit, serves to convert frequency-modulated electrical impulses generated by commutator pick-up unit A or its equivalent into a variable D. C. potential which is dependent upon the frequency only of these 'electrical impulses, and tooppose the variable D. c. potential thus produced against another potential. The diflerence between these two potentials controls the operation of circuit I. circuit III is a. full-wave rectifler and provides a source of constant-potential D. C. voltage.

circuit I includes a mld-controlled gaseous rectifler tube Il. This tube ll is energized from a secondary winding I! of a transformer 2 I. The transformer 2! is of the' multiple winding type and is powered through a primary winding 23 and lines L-l and L-2 which are conveniently energized from any conventional A. C. source, e.,g. 110 volts, cycle A. C. A fllament transformer 25, fed from `A. C. lines L-I and L-2, Supplies filament excitation for tube ll. connected in aralei with tube l'l is a diode type gas-filled rectifier tube 2 1 which also derives its fllament excitation from fllanent transformer 25. Tube 21 serves as a discharge tube for the half-wave rectiiler circuit consisting of 'tube ll, secondary winding I, wire I I, winding 1 (the D. C. load for this rectiiier) wire I: and the secondary of fllament transformer 25. since the field winding 'l pendent on the position of shaft' li.

has a relatively high inductance and since it is used in a D. C. unit, energy is stored up in this winding during the conducting period of the haliwave rectiflcation. Tube 21, although non-conducting during the conducting portion of the cycle, conducts while tube l'l is not conducting and prolongs the current through winding 1, with the result that the average current through winding 1 may be maintained substantially constant for any selected level of grid bias applied to tube l'l.

The amount otcu-rent delivered through winding 1 is dependent upon the potential difl'erence between control grid 2! of tube ll and the potential of the fllament oi tube I?. circuit I also includes a secondary transformer winding ti. a resistor 33, and a condenser :I connected in such a manneras to provide an A. C. wave of constant voltage to the grid 29 through a gridblocking resistor 31. The circuit made up of winding sl, resistor 33 and condenser Il comprises a phase shitter circuit. The phase o! this A. C. potential is held in a fixed out-ot-phase relation to the anode voltage o! tube H, due to the combined action of condenser II and resistor '33. This A. C. .potential is so connected as to ride on theD. C. bias level applied to grid Il.

The current through winding 'I supplied from circuit I can be varied in accordance, with the' D. C. potential impressed on grid !I through wire 39. The increase of this D. C. potential on grid 29 in a positive direction (with the fixed out-oI-phase A. C. wave riding thereon) in re!- erence to the potential of the fllament of tube l'l will cause 'an increase in eonduction time oi tube ll and increase the current i'iow through winding 1. A wire ll which is connected to the center-tap of the secondary of illament transformer 25 can be used to control the potential of the fllament of tube ll. The D. C. !rid potential between .wires 39 and ll, which will control the energization of winding 'I as described above, is supplied from circuit II.

The trequency-responsive or frequency-discriminatory conversion circuit II provides a D. C.

potential proportional to the frequency only oi the electrical impulses supplied to it from commutator pick-up unit A. The action of commutator pick-up unit A can be compared to that of a switch, the frequency of the closing and opening being dependent upon the rotatlonal speed of the driven shatt li. Brushes 43 are used to contact this commutator unit A and there will be either an electrically shortor opencircuit condition existing between brushes 43, de-

(The black segments indicate insulation.) A constant potential D. C. voltage that is derived from circuit m (to be described below) is present between points '45 and 41, and connected across this D. C. potential are the components oi' circuit II.

The electrical circuit of circuit section II, start- I ing at point 41, which may be considered to be of negative polarity, is as follows: wire 49, commutator pick-up unit A, wire il. a condenser Il. a diode tube 55, and resistors 51 and I'. The impedance of condenser 53 is dependent on the Irequency ot the impulses supplied by commutatorunit A. The unidirectional current conducted through tube II and load resistor I'I is dependent on the value of this impedance. The higher the impedance of condenser u, the lower will be current through tube 55 and resistor l'l.

Thus it can be seen that the frequency of the impulses generated -by commutator pick-up unit `D. C. potential. This second potential is that between point and a control arm I: of a potentiometer N. The diflerence of the variable D. C. potential between points 45 and OI and the potential between point I! and brush on II is used as a D. C. grid-control voltage tor circuit I and is impressed across wires 38 and ll. The action of such opposing D. C. potentials is explained in greater detail in United States Patent 2377384.

The constant potential D. C. voltage which is present' across potentiometer 66, i. e. between points II and 41, is supplied by circuit m. This circuit consists ot a secondary winding Il of transiormer 2l. the ends of which are connected to the anodes o! a duo-diode type rectifler tube u. The fllaments of the tube II are heated by means oi a fllament transiormer 'll powered from A. C lines L-l and L -z. The voltage developed across secondary winding 81 is rectlned by the action of the tube sa and the tull-wave rectined output is conducted by two wires 13 and 'II to a D. C. filter section comprising a choke ll, and a filter condenser 1.. The wire 'II is positive in relation to wire 'II and the D. C. potential across these wires is regulated to a constant level by action of a cold-cathode voltage regulator tube Il in conjunction with a resistor II.

operation is as follows:

It is initially assumed that the field winding 'I o! the electromagnetic clutch I has been energized and the member I is driven by some prime mover and the driven member I is mechanically loaded by apparatus driven by shalt II. It may be seen that the commutator unit A is being driven by shaft !land that the speed of its potentiometer, brus'h arm il will be then opposite' I to the potential between points 45 and CI, arm u having beenadiusted inposition. for the purpose. I! we now assume that the load increases on shaft II, or if !or that or some other reason the speed of the prime mover decreases. there will be a corresponding decrease in the speed oi shatt ll and it can be seen there will be a decrease in the irequency in the impulses generated by the commutator unit A. This decrease in irequency will cause an increase in the impedance o! the condenser !I and a decrease in the current through tube II and resistor 51. The decreased current through resistor I'l causes a decreased potential between points 4! and 0 I. The potential between point ll and potentiometer brush arm !I will then be greater than the potential between points u and l and the diflerence in these potentials will be impressed across wires 39 and ll. Thepolarity ot this potential will'be such that wire 3! is positive and wire ll is negative. This The net eflect of this action is to increase the electromagnetlc coupling between members 3 and I and cause the output shalt II to speed up until the initial balanced condition is again present between the opposed potentials of circuit 11.' An increase in the speed of the output shait, due to any changed Operating conditions will cause an inverse eflect in that described above, the` net eirect being such as to decrease the fleld current through winding 'I and thus decrease the speed oi' output shatt li.

series condenser II. resistor II and filter condenser ll have been slighty altered in Fig. 2 but their operation is the same. It will also be noted that the circuit V rectiiller supplies the D. C. voltage for resistor II in'place ot circuit m as shown in Fig. 1. This of course does not aflect the operation of circuit II.

circuit V includes a duo-diode type tube !23,

the anodes of which are connected to the ende Although all adjustments of the speed oi' the shaft I! have been described in relation to the control exercised over circuit II by the commutator pick-up unit A, control can be exercised in another convenient nianner. By manually adjusting the position of potentiometer arm 33, the

speed of the shaft !5 can be adjusted to any desired value and due to the automatic action of circuit II and commutator pick-up unit A, previously described, the speed of the 'output shalt i !5 will-be maintained at this manually set speed.

arthe secondary winding I!! 'ot transformer Il. The anodes of this tube !23 are energized through the i'llament transformer ill from the A. C.- lines L--|. L-I, The rectifled full-wave D. C. output of circuit V is filtered by a filter network comprising a 'choke I!! and a condenser III. A wire |33 supplies D. C. voltage to a photoelectric cell 39 and the plate circuits oi' tubes MALI" and lil. A- wire !35. which is negative in pclarity with respect to wire !33, completes the power circuit V byconnection with all the ground return leads of circuits II and IV. The photoelectric unit B consists of a perforated disc 81, which is driven by the output shaft ll, a light source 35, a photoelectric cell 39, a resistor 90 and wires 32 and 34. The light source 35 and cell 39 are so placed in relationship to the disc althat the light beam Broadly considered, the operation of the-circuit 4 of Fig. 2 corresponds to that of -Fig, l-and to avoid circumlocution all parts which operate similarly in both Flgs. 1 and'2 will be designated by like reference characters.

As described, the device of Fig. 1 has a commutator type pick-up unit A as 'an impulse sensitive control unit, whereas Fig. 2 employsa photoelectric unit B as the means of generating impulses of constant amplitude and varying i'requency. To adapt this type of impulse sensitive unit 'B to the circuit of Fig. 1, two additional circuit sections .IV and V are included in Fig. 2. Ccmmutator pick-up unit A alone,`or circuit IV combined with any one 40 pick-up unit such as B, A, C, D, or the pick-up unit of Fi 5 or Fig. 6, corriprises a i'reque'ncymodulator circuit. Circuit IV is a, cascade ampliiier with a peak-limiting or cllpper stage, which serves to amplify the impulses ot the photoelectric unit B and to present a constant-amplitude variable-frequency signal to circuit II.` Cir'cuitv is a full-wave rectifler unit and Supplies' thepowerequirement of circuits II, IV, and the photoelectric unit B.

ircuit IV is -provided with a set oi input terminals X and Y which are coupled to an amplifler tube s by means of a coupling condenser 03 and a grid resistor 95. The anode of tube !i is supplied with a I). C. potential through a plate load resistor 91. The output of tube !l'is coupled to clipper or limiter tube 9.9 through a coupling condenser o and a resistor !034 ;The circuit of the limiter tube 99 also includes a second resistor m.

The peak-limlted signal output of .tube 39 is transferred throughcondenser m to an ampllfler tube los, whichincludes a grid resistor III in its input network. The D. C; power for amplifier tube Io! is supplied through plate load resistor II3, and a* coupling eondenser iii transfers the voltage variations of this resistor' ||3 to the grid circuit of tube Ii'l which includes a resistor HO; Direct current is supplied to the anode z of tube Il'l through the resistor 65, this resistor being the connecting component oi circuits II and IV.

It is to be understood that circuit II functions the same as in Fig. 1, the onlydifference being that the input signal here is of more or less sinusoidal shape whereas in Flg. 1 it is of` a, more or from the source 35 will fall on the 'photoelectric cell 39 only when the disc 31 is in certain positions of its rotation'al cycle. The photoelectric unit B in conjunction with the resistor converts these intermittent flashes of light into electrical impulses, the trequency of which is dependent on the speed of the shalt s and disc 81. These electrical impulses are presented to circuit IV by Jacks x and Y which are adapted to be connected to terminals X and Y oi circuit IV.

The operation of thecircuit of Fig. 2 `is as tollows:

Assuming that the output shaftis Operating at a given speed 'and that the D. C, potential between points 45 and 3! (across resistor !1) is balanced with the opposing D. C. potential between point 45 and potentiometer arm 33. it may A be seen that'the !requer'cy of the impulses de- 45 livere'd from the photoelectric unit B will also be a given value. If the load be decreased on the-output shatt !5 (thus lncreasing its speed) there will be an increase in the !requency oi the light flashes that strike photoelectric tube 39. This will cause the 'irequency of the electrical impulses through the resistor 90' to increase and as jacks X and Y are connected to input ter- -minals X and Y, this increase in the frequency .of electrical impulses is presented to the grid of the amplifier tube Oi. The peak-limiting action tube 99 in conjunctio'n with resistor I03 prevent: any variatlon ofamplitude of the amplifled output of tube Bl. Thus a signal is coupled to the amplifler tube III! that is substantially constant in amplitude and has a i'requency which increases from that representing steady state conmtions. Tube HT further ampiiiles this signal output of tube I and the va'riable-irequency constantamplitude' of increase& irequency is impressed across resistor 53. v

.The impedance of the condenser 53 will be decreased by the increase in the irequency of thesignal across resistor Stand this in turn will cause an i'ncreased current flow through re- 7 sistor Bl which will increase the D. C. potential between point 45 and point Il. This increased potential will override the manualy selected D; CL potential between potentiometer arm 33 and point 45 and cause this dlil'erence in potential less squared-type wave form. The position of the '75 to be impressed between the grid 29 and the lila- &4492770 7 ment of the tube I'l. This potential difference (with the phased A. e. voitage waves o! resistor 8! riding thereon) is of such polarity as to drive the grid !I more negative in reiation to the fllament oi tube I'I. This decreases the conduction time of tube ll, with a corresponding decrease in current flow through winding 1. This in turn decreases the electromagnetic ooupling between members 8 and and the speed oi' the output shaft I! will decrease until the two opposed D. C. potential's of circuit II are again balanced. Bimilarly. as in the circuit'of Fig. 1, the speed of the output shaft I! may be manuaily adiusted to any desired speed by moving potentiometer arm 83 in the proper direction, and after such setting is made the speed desired will be constantly maintained. v

It should be noted that both the commutator pick-up of Fig. 1 and the disc 81 and associated parts are quite easy to apply to a shaft such as I! which is already in existence without the necessity for special gears or the like. In fact, further simpliilcation in this respect can be made in Fig. 2 by simply painting alternate light and dark regions on the shaft I! and shining a light beam thereon. The varying reflections may then be picked up by the photoelectric tube 89. This illustrates the convenience with which this type of apparatus may be adapted to machines already in existence.

As shown in Fig. 3, a piezoelectric unit C may be mounted upon the 'supporting pedestal oi the driven shat IS of a coupling. This will also' produce impulses of substantially constant amplitude and of Irequency corresponding to the vibratory frequency of shaft IS. This frequency will be in a proportion to the speed of shalt li. This is because the piezoelectric unit c of Fig. 3 is sensitive enough to pick up mechanical impulses caused by the out-of-balance condition, however slight, which is always present in machines ot the type under consideration. This unit C when connected by means of jacis X: and Ya to the two input terminals X and Y oi Fig. 2 will also supply frequency. modulated electrical impulses closely to control the output speed oi dynamoelectric apparatus to any desired value. It is understood that with such connections in Fig. 2, X and Y are disconnected. It will be clear that the piezoelectricecrystal vibration pick-up is a class example of any suitable vibration pick-up and that a magnetic type could also be used. p

Fig. 4 shows a simple variable A. C. inductor unit D which is adapted to be connected by iacks Xand Ya to input terminals X and Y of Pie. 2.

This unit is constituted by a magnetic core 2 having poies 4. Primary windings are shown at l, fed from a 60-cycle A. C. supply I. Secondary windings are shown at II and these supply the jacks X' and Ya. Fastened to the shaft I! is a magnetic armature!! having opposite teeth M. As the armature i! rotates and pairs of its teeth M intrmittently become positioned opposite the poles I, thetransformer field will be varied, thus varying thevoltage applied to the jacks X: and Ya', the latter being i'or ampliiication to the terminals X and Y in Fig. 2.' Thus this unit, when mounted onthe output shatt ii. will generate electrical impulses 'which vary in frequency with the rotational speed ot shaft` IS. The output voltage of 'sinh a unit D does, however, vary in amplitude, but' this variacion is eliminated by the' action of the clipper or limiter tube I! so that the rrequency-modulat d m ulses which are to be converted by requency-discriminatory circuit II are again substantially constant in ampiitude and dependent in :requency on the variation in the speed ot the output shatt li.

In the case of the pulsating unit shown in mg. 4. simuitaneous conditions should be avoided between the speed of the shalt il and the A. C. dr quency applied to circuit l. This can be avoided by changing the irequency of the A. C. current in circuit I or changing the angular distances between poles on the armature z, or both.

In Fig. bis shown another simple means !or obtaining impulses. This is by means oi a rotry condenser ll consisting of at least one relative y stationary plate I: and at least one rotary pinte !I driven rrom the shait ii. A battery 22 spplies D. C. voltage to the condenser. As the pinte !I moves at shait speed, impulses areapplied to the connected jacks X4 and Y. the latter being tor application to the terminals X and Y oi m. 2. With the Jacs xi and Y4 applied asstated. the operation oi the Fis. 2 circuit will be clear without iurtherdescription.

It should be understood that the invention is not limited in application to slip coupiings, but that it is applicable to the control oi a wide range ot dynamoelectrie machines. For example, in Pig. 6 there is shown a D. C. motor 24 in a D. C. circuit II. The field coil of this motor is shown at 28 and, tor control purposes, corresponds to the coiis 'I in Fig. 2 and is iedby lines H and II. That is to say. instead oi' controlling a clutch' coii l, the control is to be of motor coil 28. Therefore. coil !I is fed by the circuit of Fig. 2. To apply impulses to terminals X and Y of Fig. 2, iacks X and Ys are employed, as shown in Fig, 6, these being on opposite sides of a small resistance I! having for example a -volt drop. When the motor !I operates, there will naturaliy oocur a socalled commutator ripple current in circuit 20. This current applied to the resistance 30 causes a corresponding ripple voltage wave across the resistance 30 which is applied to the jacks' X; and Ys and thus to terminals X and Y when the jacks Xs and Ys are connected. Thus, through the circuit of Fig. 2, control -is obtained of the motor field ii', as is assumed, this field be substituted in the Fig. 2 circuit tor the field 1. The result is that the motor speed may be as eflectively controlled as has been described in respect to the speed of shaft li.

The various impulse-sensitive pick-up units described may by wiring be remotely positioned with respect to the balance of the circuit, i! desired, and thus the speed can be conveniently controlled from remote positions.

It is also to be understood that although Figs.

. 1 and 2 illustrate the Irequency-responsive reaction in circuit II as a condenser 53, an inductance could also be used and would only necessitate a few minor wiring modiflcations.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. 4

As many changes could be made in the above constructions without departing fromthe scope of the invention, it is intended that all-matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a llmiting sense.

I claim:

1. An electronic speed control for dynamoelectrio appara'tus having a rotating shaft and an exciter coir adapted variably to control the speed o! said short comprising a grid-controlled rectifler &449.779

means adapted variably to excite said cell, a trequency-modulator circuit for producing electrlcal n impulses of substantially constant amplitude proportional in irequency to the speed of the shaft. a !requency-responsive Conversion circuit !ed by said modulator circuit and adapted to produce a variable D.- C. potential dependent on the !requency oi said impulses, and a source of substantially constant D. C. potential connected in opposition to said variable D. c. potential to produce a grid controlling potential, said grid-controliing potential being applied to the grid-controlled rectifler means variably to energize said coil to maintain substantially constant the speed of said shaft.

72. An electronic speed control tor dynamoelectric apparatus having a rotating shaft and an ex,- citer coil adapted variably to control the speed of said shaft, comprising a grid-controlled rectifler means adapted variably to excite said coil. a frequency-modulator circuit for producing electrical impuisesof substantially constant amplitude proportiona in frequency to the speed of t e shaft, a frequency-responsive conversion circuit fed by said modulator circuit and adapted to produce a variable D. C. potential dependent on the frequency of said impulses. a source of substantially constant D. C. potential, connected in'opposition to said variable D. C. potential to produce a grid-controlling potential, said grid-controiling potential being applied to the grid-controlled rectifier means variably to energize said coil to maintain substantially constant the speed a of said shaft, and means for independently controlling the value of said substantially constant D. C. potential.

3. An electronic speed control i'or dynamoelectrio apparatus having a rotating shalt and a current-energized excitation coil adapted variably to control the speed oi' said rotating shalt, comprising a grid-controlled rectifler adapted variably to energize said excitation coil, a frequencymodulator circuit adapted toproduce electrical impuises of substantially constant amplitude proportional in frequency to the rotational speed of said rotating shaft, a irequency-discriminatory circuit fed by said modulator circuit and adapted' to produce a variable D. C. potential dependent upon the frequency of said electrical impulses. a manually adjustable source ot substantially constantD. C. potential connected in opposition to said variable D. C. potential to produce a gridcontrolling D. C. potential, and a phase shiiter circuit .adapted to produce a substantially constant A. C. .potential to ride' on said grid-controlling potential and to be in a fixed out-of-phase relationship with the anode voltage ot said Eridl adapted to control said end-controlled rectifler controlled rectifier, said grid-controlling potential and said A. C. riding potential* being adapted to control said grid-controlled rectifierfand thua variably to energize said excitation coil to maintain the --otational speed oi! said rot'ating shaft substantially constant, the govemed speed o! said rotating shaft being dependent on the value of the manuaily adjustable D. C. potential.

4. An electronic speed control for dynamoelectric apparatus 'having a rotating' shalt and a current-energized excita-tion coil adapted var-` iabiy to control -the speed of said rotating shalt. comprising a end-controlled rectifler adapted vanably to energlze salc. ekcltation coil, a pickup adapted to produce irequency-modulated electrical impulses proportional in frequency to the rotational speed or said rotating shalt. an amplifler system having at least one vacuum tube io adapted to amplify said i'requency-modulated electrical impulses. a peak limiter circuit including at least one vacuum tube adapted to maintain the anplitude ot said electrical impulses at a substantially constant level, a trequency-diseriminatory circuit !ed by said peak limiter circuit and adapted .to produce a variable D. C. potential dependent upon the irequency of said electrical impulses, a source of substantially constant D. C. potential connected in opposition to said variable D. C. potential to produce a grid-controlling D. C. potential. said grid-controlling potential being and thus variably :to energlze said excitation coil to maintain the rotational speed of said rota-ting shalt substantially constant.

5. An electronic speed control for dynamoelectric apparatus having a rotating shatt and a current-energlzed excitation coll adapted variably to control the speed ofsaid rotating shaf t, compr'ising a gru-controlled fctifler adapted variably to energize said excitatidn coil, a .pick-up adapted .to produce frequency-modula-ted electrical im-pulses propo' tional in frequency to the rotational speed of said rotating shaft, an amplifler system having at least one vacuum tube adapted to ampliiy said trequency-modulated electrical i impulses. a peak limiter circuit including at least one vacuum tube adapted to maintain the ampiitude of said electrical impulses at a substantially constant level, a frequency-responsive rectlfier circuit including at least one dlode rectifler .tube. at least'one resistor and a reactance, said rectifier circuit being adapted .to be series-connected with said .pick-up. said frequency-responsive rectifler circuit being responsive' to the frequency of said rrequency-modulated impulses .to produce a variable D. C. potential across said resistor, a manually adlustable source of substantially constant D. C. potential connected in oppos'ltion :to said variable D. C. potential to produce a eridcontrolling potential, and a phase shifter circuit adapted to produce a substantially constant A. C. potential .to ride on said grid-controlling poten tlai and to be in a fixed out-of-phase relationship with the an'ode voltage of said grid`-control1ed rectifler, said grid-controlling potential with said A. C, potential riding the'eon being adapted to control said sud-controlled rectiiler and thus variaby to enersize said excit-ation coil to maintain .the rotational speed oi' said rota-ting shatt substantially constant, the g-overned speed of said :rotating shef-t being dependent on :the value' of the manually adlustable D. C. potential.

6. An electronic' speed'- control for dynamo electric apparatus having a rtating shaft and a `ourrent-energized excitatlon coil adapted variably to control the speed oi' said rotating shaft, comprlsing a grid-controlled rectifler adapted variably to energize said excitation coilra variable inductor unit actuated by said rotating shaft and adapted to produce variable-trequency' electrlcal impulses proportional in irequency to the rota- L cuit !ed by said limiter circuit and adapted to produce a variable D. C. .potential dependent on the trequenoy of said electrical impulses, a source of substantialiy constant D. C. potential connected in opposltion to said variable D. C. :potential to 11 produce a grid-controiling D. C. potential, said grid-controlling pot ntial adapted to control said end-controlled rectiner and thus variably to energize said excitation coii to maintain the rota- `tiona speed of said rotating shait substantially constant.

7. An electronic speed control iodynamoelectric apparatus having a rotating shalt and a current-energized excitation coil adapted variably to control the speed oi' said rotatinc shalt. comprising a :rid-controlled rectiiier dapted variably to energize said excitation coil, a trequency-moduiator oircuit adapted to produce electrical impulses of substantially constant amplitude proporti-onal in frequency to the rotational speed oi said rotating shalt. a lrequency-responsve rectifler circuit including at least one diode rectiiier tube, at least one load resistor and a reactance series-connected with said tube and one oi said load resistors, said rectiiler circuit being seriesconnected with said modula-tor circuit, the variable D. C. potential across said resistor being dependent upon the irequency of said i requencymodulated impulses, and a source of substantially constant D. C. potential connected in opposition .to said variable D. C. potential to .produce a grid- 'controlling D. C. potential, said grid-oontrolling potential adapted to control said grin-controlled rectiiier and thus variabiy to energize said excitation coil to maintain the rotational speed of said rotating shaft substantially constant. 8. An electronic speed control' !or dynamoelectric apparatus having a rotating shaft and an exciter coil adapted variably to control the speed of said shaft, comprising a grid-controlled rectifier means adapted variably to excite said coil, commutator means driven by the shaft and producing electrical impulses' of substantiaiiy constant ampiitude proportional in irequency to the speed of the shaft. a irequency-responsive Conversion circuit fed by said impulses and adapted to produce a variable D. C. potential dependent on the frequency of said impulses, and a source of substantially constant D. C. potential connected in opposition to said variable D. C. potential to produce a grid-controlling potential. said grid-controlling potential being appied to the grid-controlled rectifler means variably to energize said exciter coil to maintain substantially constant the speed oi! said shaft.

an exciter ooil adapted variably to control the speed ot said shalt, comprising a :rid-controlled rectiner means adapted variaby to excite said coil, an inductor adapted to produce eiectrical impules proportional in !requency to the speed of the shalt. peak limiter cincuit including at least one vacuum .tube adapted to maintain ths ampiitude of said eiectrical impulse; at a substantiaiiy constant level, a irequency-responsive conversion circuit red by said limit er circuit and adapted to produce a variable D. C. potential dependent on the irequency oi said impulses, and a source of substantially constant D. C. potential connected in opposition to said variable D. C. potential to produce a grid-controlling potential. said grid-controlling potential being applied to the grid-controued rectiner means variably to energise said coil to maintain substantially constant the speed ot said chatt.

10. An 'electronic speed control for dynamoelectric apparatus having a rotating shaft andan exciter coii adapted variably to control the speed oi said shaft, comprising a and-controlled rectifler means adapted variably to excite said coil, a variable condenser responsive to shait movement tor producing electrioal impulses pro- .portiona in frequency to shalt movement, a

. frequency-responsive conversion circuit red by said impulses and adapted to produce a variable D. C. potential dependent on the !requency oi' said impulses, and a source of substantially constant D. C. potential connected in opposition to said variable D. C. potential to produce a gridcontrolling potential, said grid-controlling potential being applied to the grid-controlled rectifier means variabiy to energize said coil to maintain substantially constant the speed of said shaft.

RALPH L. JAESCHKE.

` REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,756,573 Stoller Apr. 29, 1930 1,972,689 Meye- Sept. 4, 1934 1,991,066 Staege Feb. 12, 1935 2,254,899 Laubenheimer Sept. 2, 1941 &277.284 Winther Mar. 24, 1942 

